Inclusion Criteria:

1. Histologically confirmed, relapsed or refractory mantle cell lymphoma requiring treatment.
2. No anti-cancer therapy for three weeks (6 weeks if rituximab, nitrosurea, or Mitomycin C) prior to study initiation, and fully recovered from all toxicities associated with prior surgery, radiation treatments, chemotherapy, or immunotherapy.
3. An IRB-approved signed informed consent.
4. Age greater or equal to 18 years.
5. Expected survival greater than or equal to 3 months.
6. Pre-study performance status of 0, 1, or 2 according to the World Health Organizations (WHO) criteria.
7. Acceptable hematologic status within two weeks prior to patient registration, including: Absolute neutrophil count (segmented neutrophils = bands * total White Blood Count (WBC)) greater than or equal to 1,500/mm^3; Platelets greater than or equal to 1000,000/mm^3.
8. Female patients who are not pregnant or lactating.
9. Men and women of reproductive potential who are following accepted birth control methods (as determined by the treating physician, however abstinence is not an acceptable method).
10. Patients previously on investigational Phase II anti-cancer drugs if no long-term toxicity is expected, and the patient has been off the drug for eight or more weeks with no significant post treatment toxicities observed.
11. Patients determined to have less than 25% bone marrow involvement with mantle cell lymphoma within six weeks of registration. Measurement to be determined by bilateral bone marrow biopsies. This criteria must be strictly met for adequate patient safety.

Exclusion Criteria:

1. Prior autologous or allogeneic bone marrow transplantation (ABMT) or peripheral blood stem cell (PBSC) rescue therapy.
2. Prior radioimmunotherapy.
3. Presence of Central Nervous System (CNS) lymphoma.
4. Patients with HIV or AIDS-related lymphoma.
5. Patients with pleural effusion.
6. Patients with abnormal liver function: Total bilirubin greater than 2.0mg/dL
7. Patients with abnormal renal function: serum creatinine greater than 2.0mg/dL
8. Patients who have received prior external beam radiotherapy to greater than 25% of active bone (involved field or regional).
9. Patients who have received Granulocyte colony-stimulating factor (G-CSF or GM-CSF) therapy within two weeks prior to treatment.
10. Serious nonmalignant disease or infection which, in the opinion of the investigator and/or sponsor, would compromise other protocol objectives.
11. Major surgery, other than diagnostic surgery, within four weeks.
12. Impaired bone marrow reserve as indicated by one or more of the following: a) History of failed stem cell collection. b) Platelet count less than 1000,000 cells/mm^3. c) Hypocellular bone marrow (less than 15% cellularity). d) Marked reduction in bone marrow precursors of one or more cell lines (granulocytic, megakaryocytic, erythroid).
13. Presence of leukemic phase of disease defined as peripheral blood absolute lymphocyte count of greater than 5,000/microliters.